The works of Ādi Śaṅkarācārya

Bṛhadāraṇyakopaniṣadbhāṣyam

Verse 156

यः श्रोत्रे तिष्ठञ्छ्रोत्रादन्तरो यँ श्रो-त्रं न वेद यस्य श्रोत्रँ शरीरं यः श्रोत्र-मन्तरो यमयत्येष त आत्मान्तर्याम्य-मृतः ॥ १९ ॥

In plain words

The one who lives inside your hearing, yet is nothing the ear can claim as its own, whom hearing itself never knows, whose body the ear is, who governs it from within -- that is your self, the ruler seated inside everything, and death does not touch him.

Close to the Sanskrit

He who, dwelling in the ear, is other than the ear, whom the ear does not know, whose body the ear is, who controls the ear from within -- he is your self, the inner controller, immortal.